The present invention relates generally to polarizers, and more particularly to a frequency selective polarizer based on a chiral optical fiber.
Any device that requires polarized light uses one or more polarizers. Polarizers have many industrial applications. For example, polarizers may be utilized in electro-optic modulators and laser subsystems. Of particular interest is the use of polarizers as in-line modules in optical fibers. Previously known in-line polarizers typically comprise an assembly with a first lens following a first optical fiber for collimating the light emerging from the fiber. The collimated light then passes though a polarizer plate and is then focused by a second lens into a second optical fiber. The main disadvantage of this type of polarizer is that it is relatively expensive and difficult to construct. Furthermore, the lens-based polarizer interrupts the optical fiber leading to optical loss. Finally, the lens-based polarizer introduces a device into the fiber that is larger than the fiber, thereby causing potential space and size problems.
One attempt to solve the above problems resulted in the development of another in-line fiber polarizer that was constructed by wrapping the optical fiber in several loops around a circular member before allowing the fiber to continue on its way. This arrangement eliminated some of the drawbacks of the previously known lens-based polarizerxe2x80x94for example this was a true in-line device that did not interrupt the fiber, and it was not expensive to manufacture. However, the coil-based polarizer suffered from another significant drawbackxe2x80x94the coil element around which the fiber needed to be wrapped was typically many centimeters in diameter making the coil-based polarizer very bulky and difficult or impossible to use in many applications.
Finally, none of the previously known polarizers were easily adjustablexe2x80x94changing the orientation of the resulting polarized light required re-configuration of the polarizer device.
It would thus be desirable to provide an in-line polarizer with low insertion loss that does not interrupt an optical fiber with a larger structure. It would also be desirable to provide an in-line polarizer that is inexpensive and easy to fabricate. It would further be desirable to provide an in-line polarizer than enables selective tuning of the orientation of the polarized light.